The objective of this project is to analyze the structural and regulatory features which control expression of HLA susceptibility genes contributing to Type I diabetes (IDDM). We will focus both on the genetic contributions of specific HLA class II genes on haplotypes associated with IDDM, and on the transcriptional regulation and tissue-specific expression of these genes. Specific aims include the use of allele- and locus-specific oligonucleotide probes to distinguish HLA DQ genetic variation differentially associated with IDDM; we will focus largely on the DQ3.2beta gene, a putative disease susceptibility allele previously implicated in diabetes susceptibility in order to clarify the contributions of the DQ3.2beta gene, and of other linked genes, as 'permissive' alleles in IDDM. A second aim of these studies is to test the hypothesis that variation in DQ beta promoter elements accounts for altered transcriptional regulation and/or tissue-specific expression of putative susceptibility alleles; this will be tested by a series of promoter region gene amplification, sequencing, and expression studies involving the upstream regulatory elements associated with class II genes in IDDM. Third, we will use a series of in vitro mutagenized DQ genes, expressed in human B cell lines, to study the structure-function relationships of specific nucleotide substitutions on T-cell recognition. These three Aims present an inter-related set of objectives to identify and characterize genetic, structural, and regulatory components of IDDM susceptibility which are contributed by HLA class II genes.